Although much has been written about the potential of affiliation in multi-institutional arrangements to improve hospital performance (i.e. efficiency), there is little empirical support for this assertion. Major restructuring of the hospital industry, from autononous institutions to multi-institutional arrangements, is occuring with little understanding of the actual effect of multi-institutional arrangement affiliation on hospital performance. Accordingly, the purpose of this study is to improve current understanding of hospital performance, with particular emphasis on the effect of multi-institutional arrangements on short-term, general hospitals. This study is a secondary analysis and information synthesis of data from the American Hospital Association annual surveys. A cross-sectional analysis of the performance of short-term, general, non-federal, non-state U.S. hospitals will be conducted using multiple regression techniques. Hierarchical regression models will be developed to first assess the effects of traditional predictors of hospital performance. Then, the simple effect of a dummy variable reflecting multi-institutional affiliation will be incorporated into the model. Finally, a more complex set of specific characteristics of multi-institutional arrangements will be substituted for the simple dummy variable in order to precisely decompose the component effects on hospital performance. The primary objective of this study is to more specifically assess the effect of multi-institutional arrangement affiliation on hospital performance. In particular, the study will identify those characteristics of multi-institutional arrangements which are related to higher levels of hospital performance. By studying all U.S. short-term, general, non-federal, non-state hospitals and all multi-institutional arrangements, generalization will be possible. By use of multiple regression analysis, a better understanding of the relative explanatory contribution of various predictors of hospital performance will be obtained.